refactor benchmark
 implemnt Cancel and add unittest
 add log
 add cancelable queue into RpcServer

 QPS: 363471
 QPS: 354609
 QPS: 357941
 remove uncessary code
 remove file net/rpc/rpc_service_controller.h, it's a empty file
add return value check in RpcServer

E1017 15:03:18.893529 26470 async_benchmark.cc:39] 8000000 completed in 20922 ms
QPS: 382372
 remove base/threading/wait_queue.cc
 add comment and disable Clear
 add unittest